docs: def add(self, field, val):
          "Add a sample"
          if engine.FieldDefinition.FIELDS[field]._matcher is matching.TimeFilter:
              val = self._basetime - val
  
          try:
              self.total[field] += val
              self.min[field] = min(self.min[field], val) if field in self.min else val
              self.max[field] = max(self.max[field], val)
          except (ValueError, TypeError):
              self.errors[field] += 1